1. Field of the Invention
The present invention relates to air vehicles, and more particularly to ornithopters which are those air vehicles that utilize flapping wings to sustain flight. There are basically two main categories of ornithopters; those that have mechanical power sources, and those that wholly sustain flight by human effort alone. The present invention is of the former type employing a small engine, pump, hydraulic circuitry, hydraulic cylinders, and electronics.
2. Description of the Relevant Art
Ornithopter air vehicles have been proposed since the earliest of times. They have been described in Greek fables and histories of air flight. However, unresolved problems have hindered practical development. Those without a power source that depend wholly on human physical effort to sustain flight have not been designed to give the flyer respite to go any distance or achieve any height. Dropping of such a vehicle from another aircraft assures a longer stay in the air, but in that case the aircraft becomes more a glider than an ornithopter. A difficult problem is designing the wing movement in such a manner that the flyer encounters no shock moves, while assuring the flyer complete control of the wing operation.
Previous attempted powered ornithopters have problems with weight and control, as well as with takeoffs and landings. The present invention has solved these problems.
The relevant art is discussed hereinbelow.
U.S. Pat. No. 3,498,574, issued to Ernst in 1970, relates to a fluttering wing aerial propelled apparatus suitable for carrying a man. The Ernst vehicle is operated by the pilot by manipulating a handle which opens and closes parts of a cylinder-piston unit, causing the wing to move in the direction desired by the pilot. The wing exactly follows or copies the movements of the pilot. The wing working force is supplied by fluid under pressure while the pilot works the control. Two cylinder-piston units are employed, one for each wing. The tail is moved physically by the pilot's feet.
The present invention, on the other hand, employs only one cylinder-piston for both wings, and utilizes only the retraction stroke to pull the wings downwardly. The wings are raised by a spring-like device. Also, the tail is operated by a separate double-acting fluid cylinder, which moves the tail up and down, as controlled by the pilot.
U.S. Pat. No. 544,816, issued to Lilienthal in 1895, discloses one of the earliest attempts to design an ornithopter. The vehicle was raised into the air by the flyer running into the wind, and after the vehicle was airborne it was balanced and steered by the flyer by means of a suitable movement of his body so as to displace the center of gravity.
U.S. Pat. No. 2,218,599, issued to Brunner in 1940, discloses a propulsion means for ornithopters.
U.S. Pat. No. 2,407,777, issued to Grawunder in 1946, relates to a glider having two pairs of wings which are actuated by the pilot to control the elevation of the glider as it moves through the air.
U.S. Pat. No. 2,578,845, issued to Schmidt in 1951, discloses an aircraft propelled by beating wings, having two distinct motions comprising the "beat" made by a power-driven reciprocator, and the "swing" motion made by the resistance of the air against the eccentrically-held wing blade. The "swing" motion is at right angles to the "beat" motion. The present invention differs from the Schmidt invention in many aspects. However, one main difference is in the employment of fluid cylinders. The present invention utilizes the retraction stroke of only one cylinder, while the Schmidt invention utilizes a plurality of cylinders.
U.S. Pat. No. 2,783,955, issued to FitzPatrick in 1957, relates to a craft which is suitable for travel in the air, on land, and on and under the water. It is a very complex vehicle designed to perform many functions. In contrast, the present invention is designed only to fly like a bird and is designed as simply as possible to perform this function using only the retraction stroke of only a single piston to achieve the desired movement of the wings.
U.S. Pat. No. 2,859,553, issued to Spencer in 1958, discloses a toy aircraft of the ornithopter or flapping wing type powered by a rubber band which is wound up by crank. When the crank is released, it causes the wing spars to move up and down.
U.S. Pat. No. 3,446,458, issued to Rogallo in 1969, relates to control devices for altering the membrane configuration of a flexible wing aircraft.
U.S. Pat. No. 3,817,478, issued to McDonald in 1974, relates to vehicles for gliding flight, and in particular to an air vehicle adapted for aerial flight to include a pair of hand-operated wings and a foot-operated tail.
The main feature, among others, which sets the present invention apart from any of the above patents or any known ornithopters is the design which actuates both wings simultaneously with only one hydraulic cylinder, and only with the employment of the retraction stroke of that single cylinder.